Conversion of coal by solvent extraction

ABSTRACT

SOLID FUEL OR AS SOURCE OF CARBON IN CARBON-STEAM REACTIONS.   COAL IS PARTIALLY CONVERTED BY SOLVENT EXTRACTION TO A MIXTURE OF EXTRACT, SOLVENT AND UNDISSOLVED CARBONACEOUS RESIDUE. THE MIXTURE IS SEPARATED INTO LOW SOLIDS-CONTAINING FRACTION AND A HIGH SOLIDS-CONTAINING FRACTION. THE COMPOSITION OF THE LATTER IS ADJUSTED SO THAT ITS ADMIXTURE OF SOLIDS AND LIQUID BINDER (I.E. EXTRACT AND SOLVENT) IS SUCH AS TO MAKE IT PELLETIZABLE. PELLETS ARE FORMED FROM THE PELLETIZABLE COMPOSITION, PREFERABLY IN A ROTARY DRUM AND INDURATED EITHER CONCURRENTLY WITH FORMATION OR SUBSEQUENTLY THERETO. THE INDURATED PELLETS SERVE EITHER AS

July 24, 1973 HIGH SULFUR COAL E. GORIN Filed D90. 8, 1971 I2 SOLVENT IO EXTRACTOR \ls LIGHT on.

OVERFLOW ST'LL SEPARATOR MA /-3| WASH'NG SOLVENT zo-s /EXTRACT V UNDERFLOW 5o /26 PREHEATER QUENCH WATER [Q9 r35 EN INDURATION PELLETIZING A HYDRO Low SULFUR zone KILN PLANT SCREEN RECYCLE 2 /49 RECOVERY PELLETS 47 f /48 CARBONIZATION 46 GAS ZONE CONDENSER 9- GASIFICATION GASIFIERM ZONE /43 t l TAR 44 45 INVENTOR 0 .4. ASH OUT EVERETT GORIN STEAM United States Patent 3,748,254 CONVERSION OF COAL BY SOLVENT EXTRACTION Everett Gorin, Pittsburgh, Pa., assignor to Consolidation Coal Company, Pittsburgh, Pa. Filed Dec. 8, 1971, Ser. No. 205,788

Int. Cl. C10g 1/00 US. Cl. 208-8 15 Claims ABSTRACT OF TI-E DISCLOSURE BACKGROUND OF THE INVENTION Field of the invention This invention relates to an improvement in coal conversion processes which involve solvent extraction of the coal.

Description of the prior art Air pollution regulations severely restrict the use of high-sulfur coals in power stations. In order to comply with the regulations concerning permissible S0 concentrations in power station stacks, the fuel used should have a sulfur content less than 0.5 percent by weight. The coal reserves in the United States east of the Mississippi River now supply over 90 percent of the total US. production and constitute nearly 30 percent of the total US. coal reserves. A review by the Bureau of Mines has shown that there are virtually no Eastern reserves less than 0.7 percent sulfur; 80 percent of the reserves contain more than 1.1 percent sulfur and 43 percent contain more than 3.0 percent sulfur.

Coal has already been substantially displaced by lowsulfur fuel oil in many east coast areas, but supplies of this low-sulfur fuel oil are too limited for this to become a general practice. As stated by the 1970 National Academy of Engineering review of S0 removal technology, unless the necessary technology becomes available, the country may have to choose between clean air and electricity.

There are four distinct areas in which technology already exists, but is being further developed for solving coals sulfur problems. They are (1) S0 removal from stack gas, (2) selective rejection of pyrites from the coal, (3) coal gasification, and (4) coal liquefaction.

The present invention lies in the field of coal liquefaction. The art of coal liquefaction is old. The ability to produce a substantially sulfur-free distillate from highsulfur coals has been demonstrated in German practice. The patent literature is replete with processes for converting coal to liquids. Since hydrogenation is generally involved in such conversions, some desulfurization is always effected so that a liquid is produced which has a lower sulfur content than the coal. In recent years, the emphasis on the development of such liquefaction processes has been on partial conversion of the coal. The reason is, the correlation between hydrogen requirements and depth of conversion. More hydrogen is required per unit of coal 3,748,254 Patented July 24, 1973 conversion as the depth of conversion is increased. There thus exists an economic optimum of depth of conversion which depends upon the coal usedbut is generally between 50 and weight percent of the moistureand ashfree coal.

Partial conversion of coal may be readily accomplished by solvent treatment, i.e. extraction, of the raw coal. The so-called solvent extraction processes for making distillate fuels include, but may not be limited to, three essential unit operations, namely, (1) extraction, (2) separation of extract from undissolved solid residue, and (3) hydrogenation of the extract. These three unit operations have been reasonably well demonstrated, if not in commercial practice, at least in pilot plants, the operation of which has been described in Written publications. Many patents have been issued, especially in recent years, describing such processes. Illustrative of these are my own patents, U.S. Nos. 3,018,241; 3,018,242; 3,117,921; 3,143,- 489; 3,612,594; and 3,184,401.

The commercial feasibility of any solvent extraction process for converting coal to low-sulfur liquid fuel is critically dependent upon the amount and cost of the hydrogen requirements. The amount of the hydrogen requirements will be determined by the coal selected and the three unit operations just mentioned. However, the cost of the hydrogen is another matter. The hydrogen may be purchased or it may be manufactured from the by-products or rejects of the aforementioned unit operations.

In my above-cited Pat. No. 3,018,241, for instance, I described the production of hydrogen by the devolatilization of char obtained by carbonization of the solid residue separated from the extract. Additional hydrogen must be introduced from outside the system. US. Pat. No. 3,583,- 900, granted June 8, 1971, to l. G. Gatsis, reports the use of the char obtained by the carbonization of residue from extraction to make hydrogen by the water-gas reaction. Others have recognized that the residue from the extraction operation may well serve as a feedstock for making hydrogen.

However, the use of residue from solvent extraction is not without its attendant problems, mostly stemming from the manner and extent of separation used to separate extract from solid residue. Generally, such separation is effected by filtration, or centrifugation, or sedimentation (settling), or by use of hydrocyclones. The extent of separation depends on the quality of extract desired as well as on subsequent handling of the residue. Sometimes, even when the residue is separated to dryness, that is, with essentially no adherent extract, it is not easy material to handle because of its caking tendency. This tendency is obviously promoted by incomplete separation, as with sedimentation or by use of hydrocyclones. The only commercially proven processes for making hydrogen from carbonaceous solids require a weakly caking or non-caking carbonaceous solid.

Thus, the primary object of the present invention is to provide an improved process for the conversion of coals to fuels wherein solvent extraction is employed for the partial conversion of the coals; and, in its preferred embodiment, to provide a solution to the problem of using the residue from solvent extraction as a (feedstock to gasifiers requiring essentially non-caking feedstocks.

SUMMARY OF THE INVENTION "ice The present invention is an improvement in the process for partial conversion of coal by solvent extraction which comprises, in is broadest aspects, the following essential steps:

(1) Partial separation of the extraction product at an elevated temperature in a separation zone to yield (a) a low solids-containing product which is useful per se as a fuel, or as an intermediate in the production of liquid fuels by hydrogenation, and

(b) a high solids-containing product;

(2) Adjustment of the relative proportions of solids, solvent, and extract in said high solids-containing product to yield a pelletizable product consisting essentially of solids and a liquid binder comprising said solvent and extract;

(3) Formation of pellets from said pelletizable product in a pelletizing zone; and

(4) Induration of the pellets, concurrent with or immediately subsequent to their formation. The indurated pellets may be used per se as solid fuel or as an intermediate in the production of gaseous and liquid fuels.

GENERAL DESCRIPTION Before describing the preferred embodiment of the present invention, a general description of the process in its broadest aspects is given below.

Partial extraction of the coal Any coal may be used in the process of this invention, non-limiting examples of which are lignite, bituminous coal and sub-bituminous coal. The feed coal, in a finely divided state and free of substantially all extraneous water, is subjected to solvent extraction in a suitable solvent extraction zone at an elevated temperature. The solvent extraction process may be any of the processes commonly used by those skilled in the art, for example, continuous, batch, countercurrent or staged extraction; and conducted at a temperature in the range of 300 to 500 C., a pressure in the range of 1 to 6500 p.s.i.g., a residence time in the range of 1 to 120 minutes, a solvent-to-coal ratio of 1/1 to 4/1 and, if desired, in the presence of a catalyst and/ or up to 50 standard cubic feet of hydrogen per pound of MAP (moistureand ash-free) coal.

Polycyclic, aromatic hydrocarbons which are liquid at the temperature and pressure of extraction are generally recognized to be suitable solvents for the coal in the extraction step. At least a portion of the aromatics may be partially or completely hydrogenated, whereby some hydrogen transfer from solvent to coal may occur to assist in the breakdown of the large coal molecules. Mixtures of the hydrocarbons are generally used and these may be derived [from subsequent steps in the process of this invention. Other types of coal solvent, such as oxygenated aromtaic compounds, may be added for special reasons, for example, to improve the solvent power, but the resulting mixture should be predominantly of the type mentioned.

The coal and the solvent are maintained in intimate contact at the elevated temperature until up to about 80 weight percent of the MAP feed 60211 has been converted, i.e. depolymerized, hydrogenated, etc., to a product soluble in the solvent at the temperature employed. The product, for want of a better term, is called extract even though more transpires in the conversion than simply dissolving the coal. Generally, in order to attain depths of extrac-' tion above 50 weight percent, hydrogen must be added to the coal during extraction. The hydrogen may be added by means of a hydrogen-transfer solvent of the type mentioned above, or simply as hydrogen gas.

Partial separation of the extraction product The objective of the partial separation step is to provide (a) a low solids-containing product consisting essentially of extract and solvent, with such solids as may unavoidably be present, and (b) a high solids-containing product consisting essentially of extract, solvent and solids, with the solids in the predominant amount. The partial separation may be accomplished by sedimentation, use of hydrocyclones, filtration, centrifugation, or by a combination of two or more of these unit operations. If complete, or substantially complete separation is. efiected, as might be the case if filtration is used, then extract, and perhaps some high-boiling or non-distillable liquid, must be added to the solids to serve as binder, as will be more fully described later. In any case, separation is efiiected at elevated temperatures at or close to the temperature maintained in the extraction step.

Cooling of the extraction product may result in selective precipitation of some 0 5 the higher molecular weight portions of the extract. At times, this may be done deliberately to improve the ease of separation of the solids from the extract and to improve the quality of the extract produced. The above type of selective precipitation process may be further intensified, if desired, by addition of a saturated, i.e. paraffinic or naphthenic, solvent. The precipitated extract serves also as part of the binder required in the subsequent pelletizing step.

The low solids-containing product is separately recovered for use per se as a fuel, or as an intermediate in the production of liquid fuels by hydrogenation.

Adjustment of the relative proportions of solids, solvent and extract in the high solids-containing product This step is the key step of my improved process. The primary objective of this step is to provide a high solidscontainirl-g product which is pelletizable in a pelletizing zone. The product, in order to be pelletizable, must contain sufficient binder to permit formation of the pellets. The extract itself is a viscous non-distillable material containing little or no material distillable at 400 C. and atmospheric pressure and having a softening point well above room temperature. It serves as the principal source of binder. However, the high molecular weight portion of the solvent may also serve as part of the binder. In addition, binder may be added extraneously to supplement the extract and solvent. For instance, high boiling residual oils may be used, or even coking coal, in limited amounts. When the term extract is used herein, it is intended to include extract itself and any extraneously added binder.

The composition of the high solids-containing product is adjusted with two objectives in mind; the first to provide a composition which is fiowable and the second to provide a composition which is pelletizable in the pelletizing zone. If the conditions maintained in the pelletizing zone are such as to cause volatilization of the solvent, then the feed to the pelletizing zone may be richer in solvent. But if the conditions in the pelletizing zone do not cause volatilization of solvent, then the feed must be of the necessary composition for pelletization. The pelletizable composition, that is the composition excluding any solvent that may be vaporized in the pelletizing zone, is as follows:

Weight percent Extraction residue solids 55-75 Extract and solvent 25-45 where the extract is at least 30 weight percent of the extract-solvent mix, and is preferably greater than 50 weight percent. The pellets will, of course, have substantially the same composition unless the pelletization is conducted under carbonizing conditions which result in production of some gas and tar.

To obtain the desired proportions of solids, solvent and extract in the feed to the pelletizing zone generally requires adjustment of the composition of the high solidscontaining product after it leaves the separation zone. However, part of the adjustment may be achieved in the separation zone itself if it is necessary to increase the amount of extract in the high solids-containing product. The necessary additional extract may be obtained by the addition of a precipitating solvent to the separation zone. Generally, the problem of adjustment is twofold, one of removal of extract, and the other of removal of solvent. The removal of solvent may be readily accomplished by distillation. The removal of extract to the extent desired may be efiected by Washing with solvent. Adjustment of the relative proportions of the three ingredients may also be effected by adding recycled off-size pellets made in the pelletizing zone or from other sources. Generally, such pellets will have the same composition as the rest of the feed to the pelletizing zone except for losses in the pelletizing zone due to distillation. If pelletizing is conducted under carbonizing conditions, then the recycled pellets would constitute part of the solids fed to the pelletizing zone, and as such, would be considered as part of the extraction residue solids for the purpose of the above-mentioned formulation of solids and binder.

Formation of pellets The primary objective of the pelletizing zone is to form pellets out of the flowable mass received from the separation zone after suitable adjustment of the composition as described above. The pellets may be made by any one of the many known pelletizing processes, for example, briquetting, extrusion, or agglomeration, under carbonizing or non-carbonizing conditions at a temperature above the softening point of the binder. The process selected should be one which is adapted to be used at an elevated temperature at which the extract is fluid. The size of the pellets is generally between 14 mesh Tyler Standard screen and two inches, suitable for use as a fuel or in subsequent treatments.

Induration of the pellets To be useful as fuel or as reactant, the pellets must be sufiiciently hard to permit handling without breakage or attrition. If the pellets are formed in the pelletizing zone under carbonizing conditions, that is at a temperature above 750 F., the resulting pellets will be sufiiciently hard to permit handling for almost any use. However, if no carbonization occurs in the pelletizing zone, then congelation of the pellets subsequent to the pelletizing step is required. The extract =will solidify upon cooling below the softening point of the solution of extract and solvent which is generally above 300 F. The resulting congealed pellets are of sufiicient hardness to be handled for most uses as a fuel or reactant.

PREFERRED EMBODIMENT-PRODUCTION OF LOW-SULFUR LIQUID FUELS For a better understanding of the present invention, its objects and advantages, reference should be had to the following description of the preferred embodiment of the present invention and to the accompanying drawing which illustrates schematically the preferred embodiment.

The preferred embodiment of the present invention comprises:

(1) a solvent extraction zone (sometimes called Extractor) wherein a high-sulfur coal is extracted;

(2) a separation zone 20 (sometimes called Separator) wherein the extract (sometimes called overflow) is partially separated from the residue (sometimes called underflow) (3) a distillation zone 30 (sometimes called a Still) wherein the overflow from the Separator 20 is distilled to recover solvent for recycle to the Extractor;

(4) a Washing Zone 40 and a Preheater 50 which, in combination, serve to adjust the composition of the underflow from the Separator 20 to make a pelletizable flowable mass;

(5) an agglomeration zone 60 (sometimes called Pelletizing Kiln) consisting essentially of a rotary kiln, usually slightly inclined from the horizontal, wherein pellets are formed from the suitably adjusted underflow;

(6) an Induration Zone 70 consisting of a water quench through which the pellets are passed to cool them and thereby congeal them to non-caking solids;

(7) a Gasifier 80 where a hydrogen-containing gas is produced from the pellets made in the Pelletizing Kiln; and

(8) a hydrogenation zone (sometimes called Hydro Plant) wherein the extract is hydrogenated to yield lowsulfur liquid products suitable for use as liquid fuel.

Feed coal A high-sulfur coal is preferably used in the process of this invention. Preferably, the coal fed to the process is one having a volatile matter content of at least 20 weight percent, for example, a high volatile bituminous coal such as Pittsburgh Seam coal. A typical composition of a Pittsburgh Seam coal suitable for use in the process is shown in Table I below.

TABLE I Proximate analysis: Wt. percent MF 1 coal 1 MB means moisture-free.

2NIAF means moistureand ash-free.

The feed coal is preferably ground to a finely divided state, for example, minus 14 mesh Tyler Standard screen, and is freed of substantially all extraneous water before introduction into the Extractor 10.

( 1) Solvent extraction zone The high-sulfur coal is introduced into the Extractor 10 via a conduit 12. Solvent is introduced into the Extractor via a conduit 14. The coal and the solvent react therein to yield the desired coal extract.

The preferred solvent extraction process is a noncatalytic, continuous, countercurrent process conducted in a vertical cylindrical vessel, at a temperature in the range of 300 to 500 C., a pressure in the range of 1 to 6500 p.s.i.g., a residence time in the range of 1 to minutes and a solvent-to-coal ratio of 1/1 to 4/ 1.

The preferred solvent for the coal is a polycyclic, aromatic hydrocarbon which is liquid under the temperature and pressure of extraction, and contains partially or completely hydrogenated aromatics. It is naturally derived from hydrogenation of the extract. It usually has a relatively wide distillation range with an initial atmospheric boiling point of about 450 F. and a final boiling point of 800 F. or even higher.

The coal and the solvent are maintained in intimate contact within the Extractor 10 until the solvent has extracted, i.e. converted or dissolved, 50 to 80 weight percent of the MAP feed coal. In order to attain such depths of extraction, hydrogen must be added to the coal during extraction. In this preferred embodiment, hydrogen is added by means of the solvent described above which is hydrogenated from time to time as needed.

(2) Separation zone Following extraction, the mixture of solvent, extract and residue is conducted rapidly, so as to avoid excessive cooling of the mixture, through a conduit 16 to the Separator 20. The preferred separation system is sedimentation (settling). Settling is conducted at or about 600 F. While settling may be conducted so as to effect substantially complete separation of liquid and solids, it is preferred, for the purpose of this invention, to assure an underflow which is a flowable slurry, that is, one having about 45 to 55 weight percent solids. This flowable slurry is withdrawn from the Separator 20 through a conduit 21. The overflow from the Separator is withdrawn through a conduit 22 to the Still 30.

(3) Distillation zone The overflow from Separator 20 consists of a low solids-containing product, principally extract and solvent, with less than five weight percent solids. It is fractionally distilled in the Still 30 to recover principally light oil, which is suitably recovered through a conduit 24, and at least some solvent. The solvent which boils in the range of 450 to 800 F. is withdrawn through the conduit 14 for reuse in the Extractor 10. The solvent may first be subjected to suitable hydrogenation (not shown) in conventional fashion to make it eifective as a hydrogen transfer solvent if the desired depth of extraction demands it. Extract, usually associated with a relatively small amount of solvent, is conducted through a conduit 26 to the Hydro Plant 90. The extract is substantially nondistillable without decomposition.

(4) Adjustment zone The composition of the slurry leaving the Separator 20 must be adjusted. Generally, the adjustment consists in the removal, rather than the addition, of solvent or extract, or both. Addition of either solvent or extract, if required, may be by slipstream from appropriate conduits in the plant. Removal of either solvent or extract is preferably accomplished as follows. The underflow, i.e. the settled slurry from the Separator 20, is introduced into the Preheater 50 through a conduit 31 where it is heated under pressure to an elevated temperature, 675 to 800 R, such that the necessary amount of solvent is vaporized in the Pelletizing Kiln 60. If it is desired to remove extract, then solvent from a conduit 32 is mixed with a slipstream of slurry received from a conduit 33 that is connected to conduit 31. The mixture is conducted to the Washing Zone 40 which'preferably consists of one or more hydrocyclones where a suitably controlled separation occurs between liquids and solids. The portion consisting essentially of solvent enriched with extract is returned to the Separator 20 via a conduit 34 while the portion containing substantially all the solids is returned via conduit 35 to the slurry conduit 31, or if preferred, directly to a conduit 36 which carries the mainstream of slurry from the Preheater 50 to the Pelletizing Kiln 60. By suitable regulation of the operation of the Washing Zone 40 and the Preheater 50, the composition of the underflow from the Separator 20 is adjusted to yield the previously prescribed composition.

() Pelletizing zone The pelletizing zone in this preferred embodiment is a substantially horizontal, but slightly inclined, cylindrical, rotary kiln (Pelletizing Kiln 60) which is adapted to operate at internal temperatures of 400 to 700 F., i.e. under non-carbonizing conditions. The mixture of solvent, extract and extraction residue (suitably adjusted in relative proportions as above described), is introduced into one end of the Kiln 60 along with recycle off-size solids received from a recycle conduit 37. Air is carefully excluded from the inside of the Kiln. The feed mixture is continuously fed to the Kiln. The temperature of the mixture Within the Kiln is maintained by any suitable means at a temperature between 400 and 700 F. which will assure volatilization of at least one-half the solvent contained in the feed. The resulting mixture is tumbled in the rotating Kiln to form pellets in a wellknown manner as it advances through the Kiln. The size consists of the resulting pellets is determined primarily by the ratio of liquid binder to total solids in the Kiln product.

(6) Induration zone Hot pellets are continuously withdrawn from the Kiln 60 through a conduit 38 to the Induration Zone 70. The pellets, as formed under non-carbonizing conditions, are

sticky, rather soft, and not suitable for handling, particularly for purposes of transfer. Accordingly, they are cooled sufiiciently below the melting point of the extract to eflect congelation of the liquid binder. To do this, quench water is introduced into the Induration Zone 70 by a conduit 39. The zone simply consists of water sprays which shower down onto the hot pellets. If desired, and it is more convenient, the sprays may be mounted within the exit end of the Kiln so that congelation of the pellets occurs before they leave the Kiln.

The preferred size of pellets is greater than 14 mesh Tyler Standard screen. If there are any pellets above about two inches, then it is desirable to crush them to less than two inches. The portion of the pellets (including the crushed oversize pellets) which is less than 14 mesh in size is separated, after suitable cooling, by a screen 39 and recycled through the conduit 37 to the inlet end of the Pelletizing Kiln. The pellets of desired size are conveyed through a conduit 41 to the Gasifier '80.

(7) Gasifier The Gasifier is preferably of the fixed bed type, requiring a non-caking or weakly caking carbonaceous feed for satisfactory commercial operation. In such a gasifier, a bed of pellets which are relatively stationary with respect to each other moves progressively downwardly, first through a carbonizati-on zone 42 wherein the pellets are further hardened, and then through a gasification zone 43. Steam and air (or oxygen instead of air) are introduced into the gasification zone through conduits 44 and 45, respectively, and are circulated upwardly through the downwardly moving bed. The temperatures in the carbonization zone are maintained within the range 700 to 1000 F. by the hot gases issuing from the gasification zone. The gasification zone is maintained at a temperature in the range of 1400 to 2000 F. The pressure is to 500 p.s.i.g. The incoming pellets are carbonized in the carbonization zone yielding tar vapors which are withdrawn with the effluent gas via conduit 46. Solvent liquids retained in the pellets are simultaneously distilled from the pellets. The char product moves downwardly in reactive contact with the upflowing steam and oxygen to form CO CH H CO. These pass through the carbonization zone and into conduit 46. The efiluent gas, including tar and solvent vapors, is passed into a Condenser 47 in which the tar and solvent vapors are condensed and removed. The tar-free gas is conducted by a conduit 48 to a suitable hydrogen (H recovery system 49 of conventional type, from which a hydrogen-enriched gas is recovered. This gas is conducted via a conduit 51 to the Hydro Plant 90.

(8) Hydro plant In the I-Iydro Plant, the extract introduced by conduit 26 is reacted with hydrogen in known fashion in the presence of a fluidized catalyst under the following conditions:

Reactor temperature 400 to 475 C.

Reactor pressure (total) 2000 to 6000 p.s.i.g.

Hydrogen feed rate 2000 to 42,000 s.c.f./bbl.

feed.

Liquid hourly space velocity 0.3 to 3.0 vol./vol./hr.

Vaporous products are produced which may be fractionated and condensed to yield desired low-sulfur oils of different boiling ranges.

According to the provisions of the patent statutes, I have explained the principle, preferred construction, and mode of operation of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

1. In a coal conversion process which includes partial extraction of the coal by a solvent to yield a mixture of coal extract, solvent and undissolved carbonaceous residue, the improvement which comprises:

(a) eifecting separation of said mixture into at least two parts, the first part being a low solids-containing product containing said coal extract and solvent, and the second part being a high solids-containing product containing said coal extract, solvent, and undissolved carbonaceous residue;

(b) adjusting the relative proportions of said solid residue, solvent, and coal extract in said second part to yield a flowable mass which is pelletizable in a pelletizing zone wherein said extract and solvent serve as the principal source of liquid binder;

(c) forming pellets from said pelletizable mass in a pelletizing zone; and

(d) subjecting said pellets to induration.

2. The process according to claim 1 wherein said secolnd part produced in the separation step (a) is a flowable s urry.

3. The process according to claim 1 wherein the feed coal has a size less than 14 mesh Tyler Standard screen, and the pellets formed in the pelletizing zone are between 14 mesh Tyler Standard screen and two inches.

4. The process according to claim 1 wherein the pellets are subjected to gasification in a fixed bed gasifier by reaction with steam to form CO and H and the hydrogen produced thereby is used to hydrogenate at least a portion of the coal extract contained in said first part produced in step (a).

5. The process according to claim 1 wherein said induration is effected by conducting pelletization under carbonizing conditions.

6. The process according to claim 1 wherein said induration is effected by congelation following pelletization in said pelletizing zone.

7. In a coal conversion process which includes partial extraction of the coal by a solvent to yield a mixture of coal extract, solvent and undissolved carbonaceous residue, the improvement which comprises:

(a) efiecting separation of said mixture into at least two parts, the first part being a low solids-containing product containing said coal extract and solvent, and the second part being a high solids-containing product containing said coal extract, solvent and undissolved carbonaceous residue;

(b) adjusting the relative proportions of said coal extract, solvent and residue in said second part to yield a flowable mass which is pelletizable in a pelletizing zone, the composition of said mass in said pelletizing zone being 55-75 weight percent of solids and 25-45 weight percent of liquids, wherein said coal extract is at least 30 weight percent of said liquids;

(c) forming pellets from said pelletizable mass in said pelletizing zone; and

(d) subjecting said pellets to induration.

8. The process according to claim 7 wherein the pellets are formed by tumbling said pelletizable mass in a rotating kiln.

9. The process according to claim 7 wherein said induration is effected by conducting pelletization under carbonizing conditions in said pelletizing zone.

10. The process according to claim 7 wherein said induration is effected by congelation following pelletization in said pelletizing zone.

11. A process for making liquid fuels from coal which comprises:

(a) subjecting the coal to treatment with a solvent,

whereby a mixture of extract and undissolved hydrocarbonaceous solid residue is obtained;

(b) effecting separation of said mixture into at least two parts, the first part being composed principally of extract in solvent, and the second part being composed principally of solid residue, extract, and solvent;

(c) subjecting at least a portion of the extract in said first part to hydrogenation, whereby a liquid fuel is obtained;

(d) adjusting the composition of said second part to have the following relative proportions of solid residue, extract and solvent,

Weight percent wherein the extract is at least 30 weight percent of the extract-solvent mix;

(e) forming pellets from said adjusted second part under non-carbonizing conditions;

(f) cooling said pellets to effect congelation, and there by induration;

(g) subjecting said pellets to gasification by treatment with steam to form CO and H and (h) recovering H from the gaseous product of step (e) and using at least a portion thereof to effect hydrogenation in step (c).

12. The process according to claim 11 wherein the adjustment in step (d) is effected, in part at least, by selective removal of extract and solvent.

13. The process according to claim 11 wherein the pellets are formed by tumbling the adjusted second part in a rotating kiln.

14. The process according to claim 13 wherein the pellets are formed in the rotary kiln at a temperature between 400 and 700 F.

15. The process according to claim 14 wherein the pellets are thereafter subjected to carbonization in a separate zone.

References Cited UNITED STATES PATENTS 3,317,289 5/1967 Braun et a1. 44-10 1,925,005 8/1933 Rose et a1. 44-1 3,172,823 3/1965 John et a1. 44-10 DELBERT E. GANTZ, Primary Examiner I. W. HELLWEGE, Assistant Examiner U.S. Cl. X.R. 441 B, 10 R 

